Targeted delivery of therapeutic or diagnostic agents into heart tissue, such as the myocardium for revascularization treatment is very desirable. A potential benefit of targeted delivery is that there is an increased efficiency obtained by the precise placement of the therapeutic agent. For a percutaneous transluminal approach, injection catheters have been used successfully as they can overcome problems such as obtaining access to the delivery site and transporting the therapeutic agent to the desired site. Success has also stemmed from the ability of the physician to steer the distal end of the catheter to a desired location, position the distal tip of the catheter at precisely the same location where prior measurements have indicated that the drug should be infused, extending the injection needle to a proper depth within the myocardium, and retract to enable safe repositioning and removal of the catheter.
Needle control handles are known for use in controlling extension and retraction of catheter injection needles. For example, U.S. Pat. Nos. 6,540,725 and 6,623,474, the entire disclosures of which are hereby incorporated by reference, are directed to injection catheters with needle control handles having a piston arrangement for extending and retracting the injection needle. While an adjustable thumb control allows a user to adjust the throw of the piston (which in turn adjusts the distance by which the needle can extend), a separate tool is necessary to adjust the tension of the thumb control and/or to lock the thumb control in place. To provide a tool with each catheter would be undesirable for multiple reasons, including an increase in the overall cost of the catheter and the need to sterilize the tool. Accordingly, it is desirable to provide a needle control handle whose thumb control can be readily adjusted and releasably locked in a predetermined position. It is also desirable to provide a catheter having a control handle for actuating longitudinal movement of a component relative to at least the catheter body whereby the thumb control setting the amount of the longitudinal movement can be adjusted and readily locked in a predetermined position.